Communication by facsimile is becoming increasingly important in many areas, particularly, in business communications, because documents may be sent by facsimile from point to point virtually instantaneously. The delays experienced in using other modes of sending documents, such as the postal service, are avoided in transmitting documents by facsimile. The speed with which documents can be sent from one place to another has resulted in greatly increased use of facsimile, which makes it increasingly important that an uninterrupted and reliable level of service be provided on public switched telephone networks so that successful facsimile transmission of an increasing number of documents may be accomplished without significant degrees of impairment. It, therefore, has become increasingly important that the facsimile traffic through a public switched telephone network be accurately characterized. It also has become increasingly important that any impairments of facsimile transmissions be rapidly identified and the source of those impairments be accurately determined so that corrective action may be taken.
Until now, there has been no way to monitor and diagnose, actual facsimile transmissions. There is no available monitoring equipment which obtains convenient switched access to desired portions of the traffic flowing through a public switched telephone network the measure and characterize facsimile transmissions. There is nothing available which analyzes the protocols present in facsimile transmissions and ties that analysis to impairment measurements of the page data in those transmissions. There is no currently available capability of accurately identifying network and customer premises impairments during facsimile transmissions.
Prior techniques of measuring impairments affecting facsimile transmissions involve intrusive techniques which use special test signals which are monitored to ascertain any problems with the transmissions path. This results in test conditions which do not duplicate or simulate the actual conditions experienced during real facsimile transmissions. Thus, the results obtained from these intrusive techniques may not accurately reflect the situation experienced in the course of making a facsimile call. One particularly important deficiency of intrusive testing is that actual customer premises equipment is not involved in making the intrusive tests. Therefore, problems in completing facsimile transmissions caused by the customer premises equipment will not be identified as such with these techniques. The sources of impairment, therefore, may not be accurately identified by intrusive techniques. In addition to the fact that different equipment is connected to the network, the source of those impairments may also not be found due to the artificial nature of intrusive testing. Moreover, the portion of a communications network being tested must be taken out of service to accomplish the testing in accordance with prior techniques, and thus this part of the network will be unavailable for normal use.
Prior devices which measure communications signals are not able to adequately characterize a facsimile transmission non-intrusively as the transmission takes place. Moreover, if it were attempted to use this equipment for characterizing facsimile transmissions, the equipment only would be able to obtain dedicated access to a single facsimile apparatus at a time. Thus, identification of all the possible problems in a large communications network, such as a public switched telephone network, are impossible or impractical. There has been no equipment available which is capable of conveniently measuring in any meaningful fashion facsimile traffic in a public switched telephone network so that sources of impairment to those transmissions could be effectively identified and rapid and effective corrective action could be taken.
Accordingly, there is a significant and long-standing unsatisfied need for equipment which can properly analyze actual facsimile transmissions in a public switched network.